Thoughts on this?
Sorry for the Ipod pictures, but I think the visuals tell the story. I own and use both types, so not trying to advocate either way, it just seems intuitive that clamping on the bottom would try to “open the box” at the top. . .
I sit here, and wonder about these things :big_boss: 
It’s correct - hard to argue with that. What’s your question?
I guess I wonder why manufacturers seem to gravitate toward clamping on the bottom? Is there a reason we as consumers might not be aware of?
IMHO, with hand guards like Geiselle and many others that have a very snug and tight slip fit on their barrel nuts, rail distortion is an absolute non issue when tightening the handguard retaining bolts. IMHO, the design of the hanguard ( its wall thickness in the barrel nut area and barrel nut length) contribute greatly to the handguards rigidity. I am sure USASOC would not have picked the Geiselle MK 16 handguard for their URG-I uppers if they thought its clamping or attachment method had issues or was not rigorously tested.
Copy that, thank you for the reply.
All rails that clamp on the bottom are not created equally… There aren’t many that compare to the MK 16. Most are not even close.
I agree, that’s why I did not say all bottom clamp rails were equal. I prefer handguards that have longer barrel nuts and have more material around the barrel nut area, and ideally *may * need to be thermally fit like the Hodge/ Mega wedge lock and the Geiselle’s. There are some other ones out there that seem to use a similar barrel nut clamp up method like the Geiselle’s. Even though they are not my go to handguards, I am pretty sure companies like Centurion Arms and Sionic Weapon Systems to name a few would not be using handguards with bottom bolt barrel nut clamping methods if they felt they were not up to the task at hand.
Yup; whether it’s an issue or not will depend on the design of the handguard in that area and amount of material needed to make it a non-issue. However, if you just look at the two designs, all else being equal, the top clamp would probably be the lighter of the two as it may not require as much beefing up in that area.
Exactly, if we are only talking a few ounces in handguard weight or barrel weight for that matter, I personally prefer durability, that may be something slightly heavier, over something a few ounces lighter, but may be less durable. Rail distortion caused by its clamping method can be easily checked with your rifle secured in a vice and using a magnetic base indicator coming off the verticle area or wall below the Picatinny rail above the barrel nut.
I think most of the modern, anorexic rails will fail elsewhere before they open up around the barrel nut.
Catastrophic failure wouldn’t be my concern. What’s more likely is loosing clamp torque and the handguard rotating or loosening. This could happen from heat cycles, vibration, good knock to the handguard etc.
My buddy and I each bought a set of handguards (I don’t want to mention names, but their initials were M and I) and had the exact problems you are describing, the upper box spread enough to let the handguard loosen.
This was several years ago, and they may have fixed the problem since then, but I shy away from all bottom clamp guards because of that experience.
We ended up drilling and tapping (with clamp loosened) and putting a button head cap screw on each side of the box into the barrel nut, then tightened the clamp.
The Battlefield Vegas thread bore out a similar set of failures in free float tubes with those initials.
Did you follow the directions on the MI rail? As I understand it, you’ve got to use the correct inch pounds torque values and not just tighten down to avoid the problem you experienced.
The question of clamping becomes pretty much moot when you use a fatass barrel nut. Thus, G and ALG rails (and Centurion, and BCM, etc.). /thread
Agree the G rails are rigid enough for this to be a non-issue. BCM clamps from the top, basically removing the possibility.
I don’t remember, this was when they first came out (maybe 5-6 years ago ???). These were guns that lived on an ATV running cattle, so they really get banged around. The screws we added fixed the problem, and I have a full machine shop, so it was no big deal.
But it still soured me on the concept.
